Summary:
Before:
  yield`foo`;

After:
  yield `foo`;

This reinstates commit 71d3b5cd / r307023 and fixes the logic by
introducing an explicit table of JavaScript pseudo keywords.

Reviewers: djasper

Subscribers: klimek

Differential Revision: https://reviews.llvm.org/D34953

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@307087 91177308-0d34-0410-b5e6-96231b3b80d8